Your comment illustrates the extraordinary convolutions of British political "strategy" which seems to exist in an EU-free vacuum. Or on an island, maybe?

There will not be substantially another agreement with the EU than May's, because the EU (not being the petitioner) is in a situation to lay down its law, and it is not in its interest to give away a great deal more than it has. In the case of a second A50 (after withdrawal of the first), I suggest the EU will be likely to demand more strenuous conditions than in the first instance.

If Corbyn were to believe he could use Brexiteers as a foil to rally Remainer support, leading to a snap general election, and were then to campaign against no-deal but not frankly for Remain, he would end up at least as far up his own fundament as is May currently.

Put simply, if May's "deal" is out (as it probably will be), then an anti-no-deal platform = Remain. Any notion of "negotiating" anything better is illusory.